1. Field of the Invention
The present invention relates to a human-cooperative industrial robot.
2. Description of the Related Art
In general, in order to ensure the safety of operators, industrial robots operate in an area enclosed by a safety fence which limits the entry of operators. However, recently the demand for human-cooperative robots which are configured to operate in close proximity to operators is rising. In the case of human-cooperative robots, as contact between the robot and an operator may be dangerous, the robot is configured with a sensor which can detect whether or not contact has been made between the robot and the operator. For example, a force sensor may be used to detect a contact force applied to the robot. If the detected value is greater than a specified threshold value, the robot is stopped in order to ensure the safety of the operator.
JP2006-21287A discloses a robotic system equipped with a contact force detector which detects a contact force applied to any place on a robotic arm. In this robotic system, the robot moves to avoid the detected contact force, thus preventing further harm to people or objects surrounding the robot.
In some human-cooperative robots, a lead-through operation is performed in which a position of a robot is taught manually by an operator. For example JP S59-157715 A discloses a teaching method whereby a robot is directly taught based on signals output from a force sensor. Further, JP H9-150382 A discloses a direct teaching device which is configured such that it is possible to implement direct teaching only when a servo power supply retaining switch provided on a simple teaching device and an operable button provided on a handle for teaching are both pressed.
FIG. 5 illustrates a robot 100 according to an existing related technology. The robot 100 is provided with a wrist 102 with a handle 110 which can be manipulated by an operator when lead-through operation is implemented. Moreover, the wrist 102 is further equipped with a force sensor 120 which can detect the force of the manipulation applied to the handle 110. The operator can implement lead-through operation by operating the teaching control panel 140 which is connected to the robot controller 130.
The teaching control panel 140 is provided with a servo enable switch 142. When the servo enable switch 142 is pressed continuously for a specified period of time, the servo power supply source is switched on, thereby putting the robot in an operable state. Further, when the pressing force is released, the servo power supply source is switched off and the robot's movement is stopped. On the other hand, the handle 110 has a lead-through enable switch 112 which is used to switch between an enabled state in which the lead-through operation is enabled and a disabled state in which the lead-through operation is disabled. Namely, while the servo enable switch 142 is pressed to switch the servo power supply source on, if the lead-through enable switch 112 is pressed for a specified period of time, the lead-through operation is enabled, and when the pressing force is released, the lead-through operation is disabled.
In the related art described with reference to FIG. 5, the lead-through operation cannot be performed unless both the servo enable switch 142 and the lead-through enable switch 112 are pressed at the same time. Since the weight of the teaching control panel 140 is not necessarily light, and both hands of the operator are used to simultaneously operate two switches, the burden during operating tends to be great. This reduces operational efficiency, and may also cause operational errors.
Further, if a safety unit is provided so as to stop the robot when the contact force between the robot and an operator exceeds a threshold value, it is preferable that the threshold value is sufficiently small so as to ensure the safety of operators. However, if the threshold value is too small, the robot may be unintentionally stopped when the manipulation force applied by an operator exceeds the threshold value during lead-through operation.
Therefore, there is a need for a human-cooperative industrial robot which lightens the burden of an operator when performing lead-through operation while ensuring the safety of the operator.